1. Field of the Invention
The present invention relates to a vibration detection device that detects a vibration caused by a hand movement or the like and a vibration correcting optical device internally provided with a vibration detection device.
2. Description of the Related Art
A primary cause of vibrations to which optical devices such as binoculars and photographing apparatuses such as cameras are subjected is unsteady handling by the user. As a means for correcting an image vibration or an image blur caused by such hand movement, vibration correcting optical devices have been proposed in the related art.
The following is an explanation of the operation of a vibration correcting optical device in the related art, given in reference to FIG. 12.
FIG. 12 is a block diagram showing the basic structure adopted in a vibration correcting optical device which includes a vibration detection device.
An angular speed sensor 10, which detects a vibration applied to the vibration correcting optical device, is generally constituted of a piezoelectric vibration-type angular speed sensor capable of detecting coriolis force. An output from the angular speed sensor 10 is transmitted to a reference value calculation unit 52. The reference value calculation unit 52 is a component that calculates a vibration reference value based upon the output from the angular speed sensor 10. After the reference value is subtracted from the vibration signal output by the angular speed sensor 10, the vibration signal is transmitted to an integrating operation unit 54. The integrating operation unit 54 is a component that converts the vibration signal expressed in angular speed units to a vibration angle for the vibration correcting optical device through a time integration executed on the vibration signal.
A target drive position calculation unit 56 calculates target drive position information for a blur correcting lens 80 by incorporating information such as the lens focal length with the information indicating the vibration angle obtained by the integrating operation unit 54. A drive signal arithmetic operations unit 58 calculates the difference between the target drive position information and position information indicating the current position of the blur correcting lens 80 and supplies a drive current to a coil 73 so as to drive the blur correcting lens 80 in conformance to the target drive position information.
A drive unit 70 that drives the blur correcting lens 80 includes an actuator portion that generates a drive force and a position detection sensor portion that detects the position of the blur correcting lens 80.
The actuator portion of the drive unit 70 is constituted of a yoke 71, a magnet 72 and the coil 73. The coil 73 is provided within a magnetic circuit formed by the yoke 71 and the magnet 72, and as a current is supplied to the coil 73, a force is generated at the coil 73 in accordance with Fleming's left-hand rule. The coil 73 is mounted at a lens barrel 82 housing the blur correcting lens 80. Since the blur correcting lens 80 and the lens barrel 82 are adapted to move along a direction perpendicular to an optical axis I, the blur correcting lens 80 can be driven along the direction perpendicular to the optical axis I by moving the coil 73.
The position detection sensor portion of the drive unit 70, which monitors the movement of the blur correcting lens 80, includes an infrared light emitting diode (hereafter referred to as an IRED) 74, a slit plate 76 having a slit 76a and a PSD (position sensitive device) 77.
Light emitted by the IRED 74 first passes through the slit 76a where the width of the light beam is constricted, and then reaches the PSD 77. The PSD 77 outputs a signal corresponding to the position of the light received on its light receiving surface. Since the slit plate 76 is mounted at the lens barrel 82, the movement of the blur correcting lens 80 is translated to movement of the slit 76a, which, in turn, is translated to movement of the light on the light receiving surface of the PSD 77. Thus, the position of the light received on to the light receiving surface of the PSD 77 is equivalent to the position of the blur correcting lens 80. A signal output by the PSD 77 is fed back as a position signal 78.
This type of vibration correcting optical device is effective for correcting an image blur attributable to an inadvertent hand movement of the user during, for instance, a normal photographing operation performed by the user holding the camera still. However, the camera may not always be used in a stationary state. For instance, the camera may be used by a photographer who often takes pictures by panning the camera or the camera may often be used by a photographer aboard a vehicle such as a helicopter. In addition, during a photographing operation performed with an AF camera, the composition is often modified due to AF lock after the photographic focus is set on a primary subject with the AF function. Since a camera is used in a variety of operating conditions, as described above, a vibration correcting system that can be effectively used under the varying circumstances is much needed.
The following are the requirements for a vibration correcting optical device used under various conditions.    (requirement 1) Under any circumstances, the quality of the image resulting from a photographing operation (the image quality of the picture) is superior to the quality of an image with no vibration correction.    (requirement 2) The user observing a viewfinder image does not experience any discomfort. Namely, during a photographing operation performed by holding the camera in a stationary state or performed from a vehicle, the photographer is able to verify that the vibration correction is in effect (the image appears still), whereas the photographer is able to follow the subject with ease during a panning photographing operation.
In order to meet these requirements, Japanese Laid-open Patent Publication No. H 05-142614, Japanese Laid-open Patent Publication No. H 07-261234, Japanese Laid-open Patent Publication No. H 10-213832 and Japanese Laid-open Patent Publication No. 2000-039640, for instance, propose methods for distinguishing an intended movement from an inadvertent vibration and for classifying movements into specific types (the photographer is holding the camera in the normal manner, the photographer is panning the camera, the photographer is taking pictures from a vehicle, etc.).
However, these vibration correcting optical devices in the related art do not always operate as intended by the photographer. For instance, a relatively large vibration occurring while the photographer is aboard a vehicle sometimes causes an erroneous judgment that the photographer is performing a panning photographing operation.
There is a vibration correcting optical device that allows the photographer to switch vibration correction modes through a switch operation so as to ensure that the vibration correcting optical device is always able to operate as intended by the photographer under various conditions. In this vibration correcting optical device, a different switch position is selected depending upon whether or not the camera is used for a panning photographing operation, and an automatic detection of a panning photographing operation is disallowed if the camera is not used for a panning photographing operation. However, the following problems arise when a vibration correcting optical device assumes such switch settings.
Even when the photographer is performing a normal photographing operation, he may handle the camera as in a panning photographing operation in order to search for the right composition (in order to modify the composition). However, since the switch setting at which a panning photographing operation is automatically detected is not selected for a normal photographing operation, a change in the composition results in an unnatural movement of the image and the image does not stabilize immediately after the composition is selected.
In addition, the result of the photographing operation is adversely affected (the image is blurred) in the worst-case scenario.
If the camera is operated by selecting a switch setting while the composition is being modified and selecting another switch setting after the composition has been decided upon in order to address this problem, the camera operation becomes impracticably complicated.
It is also required of a blur correcting optical system that it be capable of efficiently distinguishing a movement intended by the user, an unintentional vibration and a state in which both intended movements and unintended vibrations occur together.